To stop the timer from automatically starting (automatic rotation) you need to comment out a line from the plugin, aprox. line 257 of rotating-posts.php of the plugin (in version 1.10), specifically:
Change this:." rp_start_timer();\n"

To this://." rp_start_timer();\n"

This will prevent the timer from starting. Hiding the pause button is easy using CSS, which you’ll want to do since it won’t do anything if you disable the timer. Add this to your CSS file.

a#rp_nav_pause
{
display: none;
visibility: hidden;
}

Important note about hacking plugins: this is not an ideal approach since if you upgrade your plugin this hack will be lost. You can still upgrade the plugin but you’ll have to go back in and re-add the hack (unless the feature has been added to do this through the admin panel). For that reason you might want to disable auto update on the plugin so someone (including yourself) doesn’t accidentally update it: http://wordpress.org/support/topic/disable-update-checking-for-a-plugin?replies=4#post-2021866

A quick and easy way to handle it would be to set the “Duration between rotations” to a super long interval. Just be sure to make the value 99999999 seconds or less, otherwise the trick backfires and it actually speeds up to a flicker.